package com.hmdp.service.impl;

import cn.hutool.core.util.BooleanUtil;
import cn.hutool.core.util.StrUtil;
import cn.hutool.json.JSONObject;
import cn.hutool.json.JSONUtil;
import com.hmdp.dto.Result;
import com.hmdp.entity.Shop;
import com.hmdp.mapper.ShopMapper;
import com.hmdp.service.IShopService;
import com.baomidou.mybatisplus.extension.service.impl.ServiceImpl;
import com.hmdp.utils.CacheClient;
import com.hmdp.utils.RedisConstants;
import com.hmdp.utils.RedisData;
import org.springframework.data.redis.core.StringRedisTemplate;
import org.springframework.stereotype.Service;
import org.springframework.transaction.annotation.Transactional;

import javax.annotation.Resource;

import java.time.LocalDateTime;
import java.util.concurrent.Executor;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.TimeUnit;

import static com.hmdp.utils.RedisConstants.*;

/**
 * <p>
 *  服务实现类
 * </p>
 *
 * @author 虎哥
 * @since 2021-12-22
 */
@Service
public class ShopServiceImpl extends ServiceImpl<ShopMapper, Shop> implements IShopService {

    @Resource
    private StringRedisTemplate stringRedisTemplate;

    @Resource
    private CacheClient cacheClientl;
    /**
     * 根据id查询用户（redis实现）
     * @param id
     * @return
     */
    @Override
    public Result queryById(Long id) {
        //缓存穿透
//        Shop shop = queryWithPassTrough(id);
        //互斥锁解决缓存击穿
//        Shop shop = queryWithMutex(id);
        //逻辑过期解决击穿问题
//        Shop shop = queryWithLogicalExpire(id);
        //工具方法
        Shop shop = cacheClientl.queryWithPassTrough(CACHE_SHOP_KEY, id, Shop.class, id2 -> getById(id2), CACHE_SHOP_TTL, TimeUnit.MINUTES);
        if (shop == null){
            return Result.fail("店铺获取失败");
        }
        //7.返回
        return Result.ok(shop);
    }
    //线程池
    private static final ExecutorService CACHE_REBUILD_EXECUTOR = Executors.newFixedThreadPool( 10);
    //逻辑过期代码封装
    public Shop queryWithLogicalExpire(Long id){
        String key = CACHE_SHOP_KEY + id;
        //1.从redis查询商户缓存
        String shopJson = stringRedisTemplate.opsForValue().get(key);
        //2.判断是否存在
        if (StrUtil.isBlank(shopJson)) {
            //3.存在-返回
            return null;
        }
        //4.命中，需要判断过期时间，需要把json反序列化
        RedisData redisData = JSONUtil.toBean(shopJson, RedisData.class);
        JSONObject data = (JSONObject) redisData.getData();
        Shop shop = JSONUtil.toBean(data, Shop.class);
        LocalDateTime expireTime = redisData.getExpireTime();
        //5.判断是否过期
        if (expireTime.isAfter(LocalDateTime.now())) {
            //5.1 未过期-返回店铺信息
            return shop;
        }
        //5.2 已过期-缓存重建
        //6. 缓存重建
        String lockKey = LOCK_SHOP_KEY + id;
        //6.1 获取互斥锁
        Boolean isLock = tryLock(lockKey);
        //6.2 判断是否获取成功
        if (isLock) {
            // 6.3 成功，开启独立线程实现缓存重建(线程池)
            CACHE_REBUILD_EXECUTOR.submit(() -> {
                try {
                    //重建缓存
                    this.saveShop2Redis(id, 20L);
                } catch (Exception e) {
                    throw new RuntimeException(e);
                } finally {
                    //释放锁
                    unlock(lockKey);
                }
            });
        }

        //6.4 失败返回商铺信息
        return shop;
    }
    //互斥锁解决缓存击穿
    public Shop queryWithMutex(Long id){
        String key = CACHE_SHOP_KEY + id;
        //1.从redis查询商户缓存
        String shopJson = stringRedisTemplate.opsForValue().get(key);
        //2.判断是否存在
        if (StrUtil.isNotBlank(shopJson)) {
            //3.存在-返回
            Shop shop = JSONUtil.toBean(shopJson, Shop.class);
            return shop;
        }
        //判断命中的收否是空值
        if (shopJson != null){
            // 返回一个错误信息
            return null;
        }
        //4.实现缓存重建
        //4.1 获取互斥锁
        String lockkey =  "lock:shop:" + id;
        Shop shop = null;
        try {
            Boolean islock = tryLock(lockkey);
            //4.2 判断是否获取成功
            if (!islock){
                //4.3 失败，休眠-重试
                Thread.sleep(50);
                queryWithMutex(id);
            }
            //4.4 成功查询数据库
            shop = getById(id);
            //5.不存在-返回错误
            if (shop == null) {
                //将空值写入redis
                stringRedisTemplate.opsForValue().set(key, "", CACHE_NULL_TTL, TimeUnit.MINUTES);
                return null;
            }
            //6.存在-写入redis-返回
            stringRedisTemplate.opsForValue().set(key, JSONUtil.toJsonStr(shop),30L, TimeUnit.MINUTES);
        } catch (InterruptedException e) {
            throw new RuntimeException(e);
        }finally {
            //7.释放互斥锁
            unlock(lockkey);
        }
        //8.返回
        return shop;
    }
    //缓存穿透代码封装
    public Shop queryWithPassTrough(Long id){
        String key = CACHE_SHOP_KEY + id;
        //1.从redis查询商户缓存
        String shopJson = stringRedisTemplate.opsForValue().get(key);
        //2.判断是否存在
        if (StrUtil.isNotBlank(shopJson)) {
            //3.存在-返回
            Shop shop = JSONUtil.toBean(shopJson, Shop.class);
            return shop;
        }
        //判断命中的收否是空值
        if (shopJson != null){
            // 返回一个错误信息
            return null;
        }
        //4.不存在-查询数据库
        Shop shop = getById(id);
        //5.不存在-返回错误
        if (shop == null) {
            //将空值写入redis
            stringRedisTemplate.opsForValue().set(key, "", CACHE_NULL_TTL, TimeUnit.MINUTES);
            return null;
        }
        //6.存在-写入redis-返回
        stringRedisTemplate.opsForValue().set(key, JSONUtil.toJsonStr(shop),30L, TimeUnit.MINUTES);
        //7.返回
        return shop;
    }
    //获取锁
    private Boolean tryLock(String key){
        Boolean flag = stringRedisTemplate.opsForValue().setIfAbsent(key, "1", 10, TimeUnit.SECONDS);
        return BooleanUtil.isTrue(flag);
    }
    //删除锁
    private void unlock(String key){
        stringRedisTemplate.delete(key);
    }

    /**
     * 传人店铺id和过期时间
     * @param id
     * @param expireSeconds
     */
    private void saveShop2Redis(Long id, Long expireSeconds){
        //1.查询店铺数据
        Shop shop = getById(id);
        //2.封装过期时间
        RedisData redisData = new RedisData();
        redisData.setData(shop);
        redisData.setExpireTime(LocalDateTime.now().plusSeconds(expireSeconds));
        //3.写入redis
        stringRedisTemplate.opsForValue().set(CACHE_SHOP_KEY + id, JSONUtil.toJsonStr(redisData));
    }

    /**
     * 更新店铺信息
     * @param shop
     * @return
     */
    @Override
    @Transactional
    public Result update(Shop shop) {
        if (shop.getId()==null) {
            return Result.fail("店铺id不能为空");
        }
        //1.更新数据库
        updateById(shop);
        //2.删除缓存
        stringRedisTemplate.delete(CACHE_SHOP_KEY + shop.getId());
        return Result.ok();
    }
}
